Conventionally, bearings used in an ABS (Antilock Brake System) of a car include a rolling bearing with a sealing member, equipped with a magnetic encoder. Such rolling bearing is disclosed in Japanese Unexamined Patent Publication No. 2002-62305, and Japanese Unexamined Patent Publication No. 2004-19827.
A brief description will be made of a basic configuration of the conventional rolling bearing disclosed in the Japanese Unexamined Patent Publication No. 2002-62305, and Japanese Unexamined Patent Publication No. 2004-19827. FIG. 4 is a cross-sectional view showing a part of a conventional rolling bearing 101. Referring to FIG. 4, the rolling bearing 101 includes an outer ring 102, an inner ring 103, a ball 104 arranged between the outer ring 102 and the inner ring 103, a retainer 105 retaining the ball 104, a sealing member 106 fixed to the outer ring 102, and a magnetic encoder 107 fixed to the inner ring 103.
The magnetic encoder 107 includes a metal slinger 108 fixed to the inner ring 103, and a rubber multipolar magnet 109 mounted on an outer side surface 110 of the slinger 108. The slinger 108 and the multipolar magnet 109 are bonded and retained by an adhesive. A rotation sensor 112 provided outside the rolling bearing 101 detects a magnetic pole of the multipolar magnet 109 fixed to the inner ring 103 which rotates with a rotation shaft (not shown) to detect rotation speed of the rotation shaft.
In addition, the sealing member 106 is in sliding contact with the slinger 108 and seals the inside of the rolling bearing 101 to prevent grease sealed in the rolling bearing 101 from leaking and a foreign material from entering the rolling bearing 101.
Here, it is preferable that the multipolar magnet 109 is firmly bonded to the slinger 108 because when the bonding force between the slinger 108 and the multipolar magnet 109 is weak, the multipolar magnet 109 could come off in a short period. In this case, the outer side surface 110 of the slinger 108 to which the multipolar magnet 109 is bonded can increase in bonding force when its surface is roughened. In addition, when the multipolar magnet 109 is retained by use of baking, the surface is also preferably roughened. Meanwhile, as for the sealing member 106, it is preferable to enhance its sealing performance. In this case, the sealing performance is improved by smoothing an inner side surface 111 of the slinger 108 which is in sliding contact with the sealing member 106.
Here, the Japanese Unexamined Patent Publication No. 2002-62305 discloses a technique to differentiate surface roughness of the surface to which the multipolar magnet is bonded, from that of the surface which is in sliding contact with the sealing member by setting surface roughness of the outer side surface of the slinger to approximately Ra: 1.0 to 1.5 μm and the surface roughness of the inner side surface of the slinger to approximately Ra: 0.3 μm. Here, Ra means arithmetic mean roughness. However, in the above case, since a polishing process to differentiate the surface roughness of the slinger is needed, the cost could increase. In addition, the slinger could be deformed when the sliding surface is polished.
The Japanese Unexamined Patent Publication No. 2004-19827 discloses a technique in which the outer side surface and the inner side surface have the same surface roughness such that the surface roughness of the entire surface of the slinger is Ra: 0.3 to 0.9 μm. However, when they have the same roughness, the surface to which the multipolar magnet is bonded and the surface being in sliding contact with the sealing member do not function well in some cases.